Patent GB-632774-A (GB)
Title: Improvements in type printing telegraph systems
IPC: H04L1/18
Filed: 1940-05-06
Abstract: 632,774. Printing-telegraphy. DUUREN, H. C. A. VAN. May 6, 1940, No. 8143. Convention date, May 4, 1939. [Class 40 (iii)] In a printing-telegraph system, particularly for wireless transmission, in which the signals are transmitted as combinations of elements of different nature occurring in the same ratio in every signal, the receiving apparatus is such that the signal, if received without mutilation, is transferred to the printer, but if mutilated in transmission a series of non-operational or test signals is transmitted by an associated transmitter over the transmission path in the opposite direction resulting at the transmitting end in the repetition of the disturbed signal only if and when the non-operational signals are received correctly and otherwise in the transmission of a further set of non-operational signals in the original direction of transmission, the interchange of such signals being repeated until correct repetition is indicated, and the printer at the receiving end being rendered inoperative until the normal signal repeated by the transmitter is received. In the system described, an eightunit code is utilized and is formed by adding three elements to the usual five-unit code to obtain a balanced signal, having four marking and four spacing elements with a special arrangement in the cases of signals having five marking or spacing elements in the fiveunit code. At the transmitter, Fig. 1, a tape perforated according to the five-unit code controls relay tongues 21-25 and contacts associated with a transmitting relay 75 and the elements to be added are selected by relays 29, 30, 31, co-operating with contacts 3, 4, 5, 6 on a transmitter shaft. Relays 41, 42, 48 are not actuated when the five-unit signal has four elements of one nature, e.g. spacing elements, and in that case the relays 29, 30, 31 add three marking elements. If the five elements are all marking or all spacing, a positive or negative voltage is applied through contacts 9-13 closed simultaneously soon after the signal has been set up on the contacts associated with tongues 21 ... 25 to operate a relay 48 controlling contact members 49, 50 so that if the tongues 21 ... 25 are all in their upper or lower positions appropriate voltages are produced according to the first five elements of signals " O " and " V ". By means of contacts 51, 52 also operated by relay 48, the relays 29, 30, 31 are operated to add the appropriate elements to produce the signal " O," Fig. 2. Since these three elements added to the first five units of the signal " V," Fig. 2, form an unbalanced signal a relay 53 is operated when a contact 7 on the transmitter shaft is closed, and through contact 4, when closed, operates relay 31 to apply the appropriate voltage to produce the balanced " V ". If the original signal contains four marking signals and one spacing signal, since the relays in their normal position add three spacing signals; a balanced signal is provided and the closure of contact 7 on the shaft will not operate relay 53. If, however, the original signal has three marking signals, the closure of contact 7 energizes relay 53 and the closure of contact 5 operates relay 30 to produce the final elements of the signal III. If the signal is still unbalanced, relay 53 is again operated and, when contact 4 closes, relay 31 is actuated to transpose the final element of the signal III to form the signal II, and a further examination of the signal operates relay 53 through contact 6 to operate relay 29 to produce three marking signals to furnish a balanced signal with its three final elements as in the signal I, Fig. 2. When a mutilated signal is received at a station, apparatus associated with the receiver effects the operation of a relay S1, included in its transmitter and operating contacts 64, 65, 68, 69 to set up a I special code combination VI, Fig. 2, which is transmitted and the subsequent operation of a second relay S2 sets up by means of contacts 70-73 a second non-operational or test signal, VII, Fig. 2, which is repeated a number of times under control of a shaft which is rotated at a fraction of the speed of the main transmitter shaft. At the receiver, Fig. 4, the code elements of a signal are applied by a relay 76 to five relays 77 ... 84 and three relays 82 .. 84 corresponding to the final three elements. The first five elements of the next signal are applied to relays 85 ... 89 and the final three elements to the relays 82 ... 84 as before. If the received signal is the combination utilized to replace five-unit signals having all-marking or all-spacing elements, the relays 111, 112 and 113 are selectively operated by the three final elements of one of the two signals O, V, and subsequently either relay 115 or 116 operates so that at contact 122 or 123 negative potential is applied to all the tongues, whatever their position, and these five similar pulses are subsequently transferred to the printer mechanism. In the case of the other five-unit signal, relay 114 is operated by the selective operation of the relays 111, 112, 113 and disconnects lead 141 to open the circuit of the printer magnets. If a disturbed signal arrives, the unbalance of the elements operates a relay ST which disconnects the receiving mechanism of the printer and applies a negative voltage to a line 52, indicated at Q, to operate a start magnet 217, Fig. 7, releasing a shaft 218 which rotates at one sixth of the rate of the transmitter shaft. A voltage is applied over contacts 201, 205 to the line 145, Figs. 1, 7 operating the relay S1 to operate its contacts to set up the first warning signal. 'Subsequently, over line 144, relay S2 is operated to initiate the transmission of the second warning signal, which is repeated five times during the remainder of the rotation of the shaft 218. When the first warning signal is received at the distant station, i.e. the station transmitting the signal which was disturbed, relays 111 ... 113 are selectively operated and a circuit is completed for the magnet 217 which sets the shaft 218 of its auxiliary transmitter in rotation. Relay 213 is operated and, at contact 220, voltage is applied over contact 206 and conductor 143 to a relay T, Fig. 1, which steps the tape transmitter back through one or more steps. If the signal VI has been received correctly during the first revolution of the shaft 218, the tape transmitter completes three backward steps and voltage is then applied over contact 210 of a relay 214 which was energized during the first revolution of the shaft 218 to operate a relay S, Fig. 1, which steps the tape forward to the position in which the disturbed signal is repeated. If the signal VI from the distant station is received during the second or third revolution of the shaft 218 so that the tape receives two backward steps or a single step, relay 215 or 216 is operated so that over contacts 211 or 212 the relay S of Fig. 1 is operated twice or once, and consequently the tape is moved forward two steps or only one step, as the case may be. The operation of the system when the character and/or test signals are disturbed in one or both directions of transmission is indicated with reference to Figs. 6, 9, 10, 11 (not shown). Specification 519,633 is referred to. The Specification as open to inspection under Sect. 91 comprises also a modification of the arrangement shown in Fig. 7 which is arranged to take account of the number of component signals of the complete warning signal sent by the auxiliary transmitting device or the number of steps forward or backward which have been made by the tape transmitter at a time when the operation of the transmitting device is interrupted, e.g. by a taut tape between the perforator and transmitter or by operation of a key to interrupt the transmission. In the arrangement described the interruption of the transmitter circuit operates a relay arrangement so that impulses derived from a contact member on the shaft of the auxiliary transmitter and normally controlling the forward or backward movement of the tape transmitter are fed to a counter member carrying a shaft having contacts arranged so that when normal working is resumed the circuit of the modification of Fig. 7 is conditioned to send the appropriate signals to complete the composite test and warning signal or to effect the appropriate member of forward or backward steps. In the modified arrangement the control of the forward and backward relays (S and T) is not effected by a contact on the shaft of the main transmitter, but is dependent upon the position of the contact assembly operated by the shaft of the counter device. This subjectmatter does not appear in the Specification as accepted.